Antiplatelet aggregation principles from the stem and root bark of Melicope triphylla

Fifteen compounds including five furoquinoline alkaloids, dictamine (1), evolitrine (2), pteleine (3), skimmianine (4) and kokusaginine (5); two coumarins, imperatorin (6), phellopterin (7); four flavonoids, 3,5,8-trimethoxy-6,7;3′,4′-bismethylenedioxyflavone (8), meliternin (9), melisimplexin (10) and meliternatin (11); three sesquiterpene lactones, melicophyllone-A (12), -B (13) and -C (14); a steroid mixture of β-sitosterol and stigmasterol were isolated and characterized from the stem and root barks of Melicope triphylla. Their structures were determined by spectral analysis. Most of the isolated compounds showed potent inhibitory activity on rabbit platelet aggregation induced by arachidonic acid (100 μM) and collagen (10 μg/mL). Compounds 1, 2, 3 and 6 were found to possess medium inhibitory activity toward ADP-induced platelet aggregation. Compounds 1 and 2 also inhibited rat aorta tonic contraction induced by NE (3 μM) and K+ (80 mM) + Ca2+ (1.9 mM). On the other hand, meliternin (9) exhibited 80.6% inhibition of tonic contraction induced by high K+ (80 mM) + Ca2+ (1.9 mM).